1. Field of the Invention
The present invention relates to an image forming apparatus provided with a memory for storing image information corresponding to an original document image.
2. Description of the Related Art
Conventional copying apparatus of the digital type are capable of realizing so-called memory mode copying. Copying apparatus are known which are capable of making multiple copies, for example, wherein the original document is first read only one time and the read image data are stored in memory, such that said image data are repeatedly read from said memory until a specified number of copies has been completed.
In memory mode copying, the number of times the original document image is read is fewer than in normal copying wherein the original document is read for each single copy, thereby rapidly increasing the copy speed. Furthermore, in memory mode copying, the image orientation can be rotated 90 degrees via the memory access control, such that the orientation of the copy image can be unified relative to the copy sheet.
Copying apparatus which store the image information of original documents in the previously described manner have limited memory capacity. Therefore, such apparatus:must have a method for erasing the image data stored within said memory (memory erasure) at all times.
Conventional copying apparatus are constructed so as to automatically accomplish memory erasure when the copying process has been completed, or after a predetermined time period has elapsed thereafter (the length of said time period being constant). A conventional copying apparatus of this type is disclosed in Japanese Patent Application No. 60-190069.
Heretofore, the mode of use of a copying apparatus in a typical office, for example, was limited insofar as the ease of use of said copying apparatus had to be appropriate for all users in the office, although said users actually had different needs regarding the number of copies, mode of operation and the like. Thus, memory erasure was accomplished at uniform points in time.
However, from the standpoint of information security, users handling confidential documents desire to implement memory erasure after completing their copying operation. Furthermore, when a user needs to execute a copying operation wherein the number of sheets of the original document exceeds the memory storage capacity of the apparatus, said original document must be divided such that each subset of the original document contains a plurality of sheets. In such a case, the processing (setting the originals in the tray and the like) must be repeated for each subset of sheets in a continuous operation, and it is desirable that memory erasure be accomplished when copying is completed so as to improve efficiency.
In contrast to the aforesaid circumstance, users who frequently use the multiple copy operation when preparing large volume materials having a plurality of portions which exceed the number of available sorter bins will find memory erasure when the copying operation is completed (in this instance, at the completion of each multiple copy cycle) unsuitable from the perspective of the content is of said operation wherein the multiple copy operation for a number of document portions less than the number of available bins must be repeated a number of times. In such circumstances, it is desirable that the copying apparatus be capable of continuously storing the image information only for a time period specified by the user after the completion of the copying operation.
An operation key is provided for specifying memory erasure. Although copying apparatus constructed so as to accomplish memory erasure when said operation key is depressed have been considered, such operation is troublesome inasmuch as memory erasure must be specified each time a user uses said copying apparatus. Furthermore, information security is breached if a user forgets to specify memory erasure.